Overview
ISO 16610-28:2016 - "Geometrical product specifications (GPS) - Filtration - Part 28: Profile filters: End effects" defines methods for treating end effects that occur when applying linear profile filters to finite measured profiles. The standard addresses unwanted changes in filtration response at the profile ends (the end effect regions) and specifies practical correction techniques so that low-pass and other linear filters behave predictably over the full traversing length.
Key topics and technical requirements
- Scope: Applies to linear, shift‑invariant profile filters with a local weighting function (for example the standardized Gaussian filter). It provides correction methods where end effects are significant.
- End effect region: The portions at the start and end of a finite profile where the filter kernel extends beyond the measured data and causes distortion.
- Correction methods (major types):
- Zero padding - extend the profile with zeros outside the measured range (simple but can fail for profiles with slope).
- Linear extrapolation - fit least‑squares lines in end regions and extend the profile using those lines; better for sloped profiles.
- Symmetric extension - reflect the profile at ends, either line (horizontal) or point (horizontal + vertical) symmetry.
- Moment retainment criterion - modify the filter weighting locally so the filter keeps vanishing moments up to order n; this preserves polynomial components (e.g., slopes) and provides mathematically consistent end corrections.
- Automatic correction: Some filter types (linear spline filters and Gaussian regression filters per ISO 16610-22, -31, -32) inherently include end effect correction; Annex A shows corresponding weighting functions.
- Recommendations: The standard includes guidance on default corrections and how to designate applied corrections for traceable specifications.
Practical applications and who uses ISO 16610-28
- Metrology laboratories and quality assurance teams performing surface texture and profile analysis to ensure consistent filtering across full traverse lengths.
- Measurement software developers implementing profile filters (Gaussian, spline, regression) who need standardized end‑effect handling.
- CMM and profilometer manufacturers integrating filtering algorithms into instruments and firmware.
- Process engineers and research labs analyzing features where end regions could bias computed roughness parameters or reference lines.
Benefits include consistent, reproducible filtration results, better approximation of slopes and arcs at profile ends, and harmonized reporting of filtration choices.
Related standards (normative references)
Keywords: ISO 16610-28, end effects, profile filters, filtration, GPS, Gaussian filter, spline filter, moment retainment, zero padding, linear extrapolation, symmetric extension.
Open preview (PDF)Geometrical product specifications (GPS) — Filtration — Part 28: Profile filters: End effects